About an hour later, @CoveGuardians said: "First dolphin murder of the drive hunt season is complete as dead bodies are dragged to Taiji butcherhouse."

There were no details on the number of kills.

The local fishermen's association said they could not immediately confirm the report.

The campaigners are streaming live footage of a secluded bay, into which local fishermen corral hundreds of dolphins for slaughter, a practice that thrust the small town into the global spotlight in 2010 when it became the subject of the Oscar-winning documentary "The Cove".

Defenders say it is a tradition and point out that the animals it targets are not endangered, a position echoed by the Japanese government.

They say Western objections are hypocritical and ignore the vastly larger number of cows, pigs and sheep butchered to satisfy demand elsewhere.

But critics of the practice say there is insufficient demand for the animals' meat, which in any case contains dangerous levels of mercury.

The annual dolphin hunting season opened on September 1, and is expected to continue until the end of February.